Celtic F.C. suffered a heavy 4-1 defeat at the hands of VfB Stuttgart in the first leg of their UEFA Europa League knockout playoff tie, handing Martin O’Neill his first loss of his second stint in charge this season.

The opening goal arrived in the 15th minute following a sloppy clearance from Celtic goalkeeper Kasper Schmeichel. Stuttgart capitalised, with Bilal El Khannouss finishing a flick-on from Deniz Undav, as Schmeichel allowed the tame shot to slip past him.

Celtic briefly equalised five minutes later, courtesy of a major defensive error by Stuttgart captain Atakan Karazor. His misdirected pass across the edge of his own box was intercepted by Benjamin Nygren, who rounded the onrushing Stuttgart goalkeeper Alexander Nübel and slotted home.

However, parity lasted only briefly. Before the half-hour mark, El Khannouss struck again, nodding home unmarked from six yards off Angelo Stiller’s deflected cross, leaving Celtic’s defence exposed.

Celtic struggled to create meaningful chances in the first half. Stuttgart came close through Ermedin Demirovic, who saw a flicked effort saved by Schmeichel, while Jamie Leweling’s powerful shot narrowly missed.

The second half started with Celtic showing more urgency, but Stuttgart extended their lead just before the hour mark. Leweling’s low strike found the net, though Schmeichel might have done better to keep it out.

Demirovic thought he had added a fourth after linking up with Undav, but the goal was ruled out for offside. Celtic’s Nygren forced a diving save from Nübel, while Tiago Tomas tested Schmeichel later, before scoring deep into stoppage time.

With a 4-1 deficit, Celtic face a steep uphill battle in next week’s second leg at Celtic Park. The Scottish champions are now winless in their last five UEFA Europa League knockout fixtures, leaving their hopes of overturning the tie in jeopardy.